Electronic apparatus and printed wiring board

ABSTRACT

According to an aspect of the present invention, there is provided a printed wiring board including: a substrate including an edge and a fixing hole located adjacent to the edge, the fixing hole configured to receive a bolt; and a land formed in a vicinity of the fixing hole and extending in at least a first direction and a second direction, the first direction being a direction from the fixing hole toward a center of the substrate, the second direction being direction along the edge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/032,546 filed Feb. 22, 2011, which is a continuation of U.S. patentapplication Ser. No. 12/470,370 filed May 21, 2009, which is based uponand claims the benefit of priority from Japanese Patent Application No.2008-232390, filed on Sep. 10, 2008, the entire contents of each ofthese applications is incorporated herein by reference.

BACKGROUND

1. Field

An aspect of the present invention relates to a printed wiring boardhaving lands and an electronic apparatus equipped with it.

2. Description of the Related Art

For example, a printed wiring board is disclosed in which lands forgrounding are disposed around fixing holes for bolting of the printedwiring board. This printed wiring board is equipped with a substrate,the fixing holes which penetrate through the substrate, the lands whichare donut-shaped and are formed around the respective fixing holes onthe surface of the substrate, and cream solder members which are printedon the surfaces of the lands.

In printed wiring boards of this type, usually, the surfaces of thelands are subjected to solder plating to prevent corrosion of the landsand attain reliable grounding. A printed wiring board having a costadvantage over ones in which the lands are subjected to solder platingis provided by supplying solder also to the land surfaces when creamsolder is supplied to mounting patterns of other components (seeJP-A-2000-244080, for instance).

In recent years, with the increase in miniaturization and functionalityof digital equipment, the high-density mounting on a printed wiringboard and the securing of a wide mounting area have come to be requiredincreasingly. However, the above donut-shaped lands raise a problem thatthe mounting area on the printed wiring board is reduced by areascorresponding to the spaces for formation of the lands. For anotherthing, to secure a wide mounting area on a printed wiring board, it iseffective to locate the fixing holes as close to the outer periphery ofthe board as possible. However, in the printed wiring boards, the fixingholes cannot be located sufficiently close to the outer peripherybecause margins for formation of the donut-shaped lands need to besecured around the respective fixing holes.

Each of these margins needs to be set taking into consideration not onlythe space for formation of the land but also a variation that may occurwhen a land pattern is formed by etching. This is because if a land isformed in contact with the periphery the land is exposed in an end faceof the printed wiring board, as a result of which the printed wiringboard may be short-circuited with another component. This also requiressufficient margins around the respective fixing holes.

On the other hand, one method for reducing the above margins is tonarrow the widths of the donut-shaped lands. However, if the land widthsare narrowed, a land pattern may be disconnected due to a variation informing the pattern. Furthermore, since the lands are reduced instrength, the land patterns are prone to peel off when bolting isperformed through the fixing holes.

For the above reasons, the printed wiring boards cannot sufficientlysatisfy the recent requirements of high-density mounting and securing ofa wider mounting area.

SUMMARY

According to an aspect of the invention, there is provided a printedwiring board including: a substrate including an edge and a fixing holelocated adjacent to the edge, the fixing hole configured to receive abolt; and a land formed in a vicinity of the fixing hole and extendingin at least a first direction and a second direction, the firstdirection being a direction from the fixing hole toward a center of thesubstrate, the second direction being direction along the edge.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A general architecture that implements the various feature of thepresent invention will now be described with reference to the drawings.The drawings and the associated descriptions are provided to illustrateembodiments of the present invention and not to limit the scope of thepresent invention.

FIG. 1 is an exemplary perspective view of a portable computer accordingto a first embodiment;

FIG. 2 is an exemplary sectional view, taken in a horizontal plane, of amain body unit of the portable computer shown in FIG. 1;

FIG. 3 is an exemplary plan view of a printed wiring board which ishoused in a casing of the main body unit shown in FIG. 2;

FIG. 4 is an exemplary sectional view, taken in a vertical plane, of theprinted wiring board shown in FIG. 3;

FIG. 5 is an exemplary plan view of a printed wiring board of a portablecomputer according to a modification of the first embodiment;

FIG. 6 is an exemplary plan view of a printed wiring board of a portablecomputer according to a second embodiment;

FIG. 7 is an exemplary sectional view, taken in a vertical plane, of theprinted wiring board shown in FIG. 6;

FIG. 8 is an exemplary plan view of a printed wiring board of a portablecomputer according to a third embodiment;

FIG. 9 is an exemplary plan view of a printed wiring board of a portablecomputer according to a fourth embodiment;

FIG. 10 is an exemplary perspective view of a printed wiring board whichis housed in a casing of a hard disk drive according to a fifthembodiment; and

FIG. 11 is an exemplary sectional view, taken in a vertical plane, ofthe printed wiring board shown in FIG. 10.

DETAILED DESCRIPTION

An electronic apparatus according to a first embodiment will bedescribed below with reference to FIGS. 1 to 4. As shown in FIG. 1, aportable computer as an example electronic apparatus is a so-callednotebook personal computer. A description will be made with a notationthat the forward direction and the backward direction are denoted byarrows F and R, respectively.

As shown in FIG. 1, the portable computer 11 is equipped with a mainbody unit 12, a display unit 13, and hinge mechanisms 14 which connectthe main body unit 12 and the display unit 13. Supporting the displayunit 13, the hinge mechanisms 14 make it possible to rotate the displayunit 13 with respect to the main body unit 12. The display unit 13 has adisplay 15 and a cover 16 surrounding the display 15. The display 15 isa liquid crystal display, for example.

The main body unit 12 has a casing 21 made of a synthetic resin, akeyboard 22, a touch pad 23 which is a pointing device, and buttons 24.As shown in FIGS. 2 and 4, the main body unit 12 also has, inside thecasing 21, a printed circuit board 25 and bolts 26 for fixing of theprinted circuit board 25 to the casing 21. The printed circuit board 25has a printed wiring board 31 and plural circuit components 32 which aremounted on the printed wiring board 31. The plural circuit components 32include a CPU and a north bridge. The bolts 26 are not illustrated inFIG. 2. The inside surfaces of the casing 21 are uniformly covered witha conductive ground layer 46. The ground layer 46 prevents outwardleakage of electromagnetic waves from the portable computer 11.

For example, the printed wiring board 31 is a copper-clad laminationplate in which plural copper wiring layers are laminated. The printedwiring board 31 has a substrate 33 and a land 34 which is formed on thesubstrate 33. The substrate 33 is formed by alternately laminatinginsulating layers (base members) made of a glass-cloth-incorporatedresin and wiring layers sandwiched between the insulating layers. Thesubstrate 33 has a first edge 35A and a second edge 35B which definepart of the periphery of the substrate 33, a fixing hole 36 which islocated adjacent to the first edge 35A and the second edge 35B, and aconductive plating member 37 which covers the inside surface of thefixing hole 36. The fixing hole 36 is located as close to the first edge35A and the second edge 35B as possible.

As shown in FIGS. 3 and 4, the plating member 37 is made of a metalmaterial, assumes a cylindrical shape, and is electrically connected toa ground member 41 which is disposed inside the substrate 33. Theplating member 37 is continuous with and is electrically connected tothe land 34. The ground member 41 is grounded to the ground layer 46 viathe plating member 37 and the bolt 26.

The substrate 33 has, in addition to the fixing hole 36, through-holes42 for bolting of the printed wiring board 31 to the casing 21. A secondland 43 having a conventional shape (i.e., a donut shape) is formedaround the opening of each through-hole 42. When the printed circuitwiring 31 is fixed to the casing 21, the bolts 26 are inserted throughthe fixing hole 36 and the through-holes 42.

The substrate 33 has, on its top surface, a pair of first regions 44which extend along the respective edges 35 so as to assume band shapes.The land 34 is formed around (in a vicinity of) the fixing hole 36. Theland 34 extends from the fixing hole 36 in a range that is definedbetween a direction D1 from the fixing hole 36 toward a central portion45 of the substrate 33 and directions D2 along the respective edges 35.That is, the land 34 is sector-shaped and is formed so as to extendtoward the central portion 45 of the substrate 33. An angle of thesector shape of the land 34 is about 90 degrees. The land 34 ispositioned outside the first regions 44. For example, the land 34 isformed into the sector shape by etching the surface copper foil layer ofthe substrate 33.

Although in the embodiment the plural through-holes 42 and the onefixing hole 36 are provided, the invention is not limited to such acase; plural fixing holes 36 may be provided so as to replace part ofthe through-holes 42. In the embodiment, the fixing hole 36 is locatedadjacent to the two edges 35A and 35B, that is, the corner edge, of theprinted wiring board 31 and the sector-shape angle of the land 34 isequal to about 90 degrees. However, the invention is not limited to sucha case. As shown in FIG. 5, the fixing hole 36 may be located adjacentto one edge 35 of the printed wiring board 31, in which case thesector-shape angle of the land 34 is equal to about 180 degrees(described later in detail).

In the first embodiment, the printed wiring board 31 is equipped withthe substrate 33 having the edges 35 which define part of the peripheryof the printed wiring board 31 and the fixing hole 36 which is locatedadjacent to the edges 35 and through which the bolt 26 is inserted andthe land 34 which is formed around the fixing hole 36 and extendsoutward from the fixing hole 36 in the range that is defined between thedirection D1 going from the fixing hole 36 toward the central portion 45of the substrate 33 and the directions D2 that are along the edges 35.

With this structure, the land 34 is formed along the direction D1 whichgoes toward the central portion 45 of the substrate 33 and the land 34is not formed between the fixing hole 36 and the edges 35. As a result,no space for formation of the land 34 is required between the fixinghole 36 and the edges 35 and hence the fixing hole 36 can be located asclose to the edges 35 as possible. Therefore, a wide mounting area canbe secured on the printed wiring board 31, which makes it possible tocope with the miniaturization of the printed wiring board 31 flexibly.Furthermore, since the land 34 need not be formed narrowly, a landpattern can be made sufficiently strong. This prevents a phenomenon thatthe land 34 is so weak that its pattern peels off when the bolt 26 isinserted through the fixing hole 36 for the purpose of fixing. Anotherproblem can be prevented that a pattern of the land 34 is disconnectedhalfway when it is formed by etching.

The land 34 is formed outside the band-shaped first regions 44 whichextend along the edges 35. This structure prevents a problem that theland 34 is deviated to be exposed in an end face of the printed wiringboard 31. This makes it possible to locate the fixing hole 36 evencloser to the edges 35. Therefore, an even wider mounting area can besecured on the printed wiring board 31.

The land 34 has the sector shape whose virtual apex is located in thefixing hole 36, and extends toward the central portion 45. With thisstructure, the land 34 is given sufficient strength though it is simplein shape. In particular, since the land 34 has the sector shape, thehead of the bolt 26 can easily be brought into contact with the land 34,whereby the printed wiring board 31 can be grounded to the ground layer46 of the casing 21 reliably.

In the embodiment, the printed wiring board 31 is provided with theconductive plating member 37 which covers the inside surface of thefixing hole 36 and is continuous with the land 34. With this structure,the contact area between the bolt 26 and the land 34/plating member 37is increased, whereby the printed wiring board 31 can be grounded to theground layer 46 of the casing 21 more reliably.

A modification of the portable computer 11 according to the firstembodiment will be described below with reference to FIG. 5 (differenceswill be described mainly). In FIG. 5, members having the same members inthe first embodiment are given the same reference symbols as the latter.

As shown in FIG. 5, a printed wiring board 31 has a substrate 33 and aland 34 which is formed on the substrate 33. The substrate 33 has anedge 35 which defines part of the periphery of the substrate 33, afixing hole 36 which is located adjacent to the edge 35, and aconductive plating member 37 which covers the inside surface of thefixing hole 36. The fixing hole 36 is located as close to the edge 35 aspossible.

The substrate 33 has, on its top surface, a pair of first regions 44which extend along the edge 35 so as to assume band shapes. The land 34is formed around (in the vicinity of) the fixing hole 36. The land 34extends outward from the fixing hole 36 in a range that is definedbetween a direction D1 going from the fixing hole 36 toward a centralportion 45 of the substrate 33 and directions D2 that are along the edge35. That is, the land 34 is sector-shaped and is formed so as to extendtoward the central portion 45 of the substrate 33. The angle of thesector shape of the land 34 is about 180 degrees. The land 34 isdisposed outside the first regions 44.

According to the modification of the first embodiment, a wide mountingarea can be secured on the printed wiring board 31 even in the casewhere the fixing hole 36 is located in the vicinity of one edge 35.Furthermore, since the land 34 does not overlap with the band-shapedfirst regions 44 which extend along the edge 35, a phenomenon that theland 34 is deviated to be exposed in an end face of the printed wiringboard 31 can be prevented.

Next, a portable computer according to a second embodiment will bedescribed with reference to FIGS. 6 and 7. The portable computer 11 asan example electronic apparatus according to the second embodiment isthe same as that according to the first embodiment except that a printedwiring board 51 is not provided with the plating member 37 andthrough-hole plating members 52 which connect a land 34 to the groundmember 41 are provided separately from a fixing hole 36. Therefore,members that are different than in the first embodiment will mainly bedescribed below, and members having the same members in the firstembodiment will be given the same reference symbols as the latter andwill not be described.

The printed wiring board 51 of the portable computer 11 according to thesecond embodiment has a substrate 33, the land 34 which is formed on thesubstrate 33, and the through-hole plating members 52 which connect theland 34 to the ground member 41. The through-hole plating members 52 areseparate from the fixing hole 36. The substrate 33 has, on its topsurface, a pair of first regions 44 which extend along edges 35 so as toassume band shapes. The land 34 is formed around (in the vicinity of)the fixing hole 36. The land 34 extends outward from the fixing hole 36in a range that is defined between a direction D1 going from the fixinghole 36 toward a central portion 45 of the substrate 33 and directionsD2 that are along the edges 35. That is, the land 34 is sector-shapedand is formed so as to extend toward the central portion 45 of thesubstrate 33. The angle of the sector shape of the land 34 is about 90degrees. The land 34 does not overlap with the first regions 44.

According to the second embodiment, a wide mounting area can be securedon the printed wiring board 51 as in the first embodiment even in thecase where the plating member 37 is not provided. Furthermore, amanufacturing process can be made simpler than in the printed wiringboard 31 according to the first embodiment by a degree corresponding tothe elimination of the plating member 37.

Next, a portable computer according to a third embodiment will bedescribed with reference to FIG. 8. The portable computer 11 as anexample electronic apparatus according to the third embodiment is thesame as that according to the first embodiment except for the shape of aland 72 of a printed wiring board 71. Therefore, members that aredifferent than in the first embodiment will mainly be described below,and members having the same members in the first embodiment will begiven the same reference symbols as the latter and will not bedescribed.

The printed wiring board 71 of the portable computer 11 according to thethird embodiment has a substrate 33 and the land 72 which is formed onthe substrate 33. The substrate 33 has, on its top surface, a pair offirst regions 44 which extend along edges 35 so as to assume bandshapes. The land 72 is formed around (in the vicinity of) the opening ofa fixing hole 36. The land 72 extends outward from the fixing hole 36 ina range that is defined between a direction D1 going from the fixinghole 36 toward a central portion 45 of the substrate 33 and directionsD2 that are along the edges 35. The land 72 is disposed outside thefirst regions 44 or a second region 73 that is located between thefixing hole 36 and the central portion 45. More specifically, the land72 extends outward from the fixing hole 36 in two directions that arealong the edges 35 so as to generally assume an L shape as a whole. Theland 72 is continuous with a plating member 37.

In the third embodiment, the land 72 is disposed outside the secondregion 73 which is located between the fixing hole 36 and the centralportion 45. With this structure, the second region 73 can be used as amounting area; for example, interconnections and circuit components canbe disposed in the second region 73. Therefore, a wider mounting areacan be secured on the printed wiring board 71 than even on the printedwiring board 31 of the first embodiment. Furthermore, since a pattern ofthe land 72 is formed by, for example, etching a copper foil, themanufacturing process is not made more complex than in the firstembodiment.

Next, a portable computer according to a fourth embodiment will bedescribed with reference to FIG. 9. The portable computer 11 as anexample electronic apparatus according to the fourth embodiment is thesame as that according to the second embodiment except for the shape oflands 82 of a printed wiring board 81. Therefore, members that aredifferent than in the second embodiment will mainly be described below,and members having the same members in the second embodiment will begiven the same reference symbols as the latter and will not bedescribed.

The printed wiring board 81 of the portable computer 11 according to thefourth embodiment has a substrate 33, the lands 82 which are formed onthe substrate 33, and through-hole plating members 52 which connect therespective lands 82 to a ground member 41. The substrate 33 has, on itstop surface, a pair of first regions 44 which extend along edges 35 soas to assume band shapes. The lands 82 are formed around (in thevicinity of) the opening of a fixing hole 36. The lands 82 extendoutward from the fixing hole 36 in a range that is defined between adirection D1 going from the fixing hole 36 toward a central portion 45of the substrate 33 and directions D2 that are along the edges 35. Thelands 82 are disposed outside the associated first regions 44.

The land 82 is located outside a second region 73 that is locatedbetween the fixing hole 36 and the central portion 45. Morespecifically, the lands 72 extend outward from the fixing hole 36 in tworespective directions that are along the edges 35. In this embodiment,the lands 82 are disposed separately at the two positions around thefixing hole 36.

In the fourth embodiment, the lands 82 do not overlap with the secondregion 73 which is located between the fixing hole 36 and the centralportion 45. With this structure, as in the third embodiment, a widermounting area can be secured on the printed wiring board 81 than even onthe printed wiring board 51 of the second embodiment. Furthermore, themanufacturing process is not made more complex than in the secondembodiment even if the lands 82 have the above-described shapes.

Next, an electronic apparatus according to a fifth embodiment will bedescribed with reference to FIGS. 10 and 11. The fifth embodiment isdirected to a case that the invention is applied to a hard disk drive 91which is an example electronic apparatus. Although individual componentsof the hard disk drive 91 are different in structure than in the firstto fourth embodiments, the structure of a printed wiring board 51 isapproximately the same as in the second embodiment. Therefore, membersthat are different than in the second embodiment will mainly bedescribed below, and members having the same members in the secondembodiment will be given the same reference symbols as the latter andwill not be described.

The hard disk drive 91 is equipped with a casing 21, a printed circuitboard 25 which is housed in the casing 21, a housing 92 which housesplural disks, a spindle motor 93 for rotationally driving the pluraldisks, and other components. The hard disk drive 91 also has bolts 26(not shown in FIG. 10) for fixing of the printed circuit board 25 to thecasing 21. The printed circuit board 25 has the printed wiring board 51and plural circuit components (not shown in FIGS. 10 and 11) which aredisposed on the printed wiring board 51.

The printed wiring board 51 is different from that of the secondembodiment in that the former has an opening 94 where the spindle motor93 is disposed, they are the same in structure in the other points. Asubstrate 33 of the printed wiring board 51 has one fixing hole 36around which a sector-shaped land 34 is formed and two through-holes 42around which donut-shaped second lands 43 are formed, respectively. Theland 34 is the same as that of the second embodiment.

According to the fifth embodiment, even in the hard disk drive 91 whichis an example electronic apparatus, the fixing hole 36 can be located asclose to the edges 35 as possible and hence a wide mounting area can besecured on the printed wiring board 51. This makes it possible to copewith the miniaturization of the printed wiring board 51 flexibly and tothereby miniaturize the hard disk drive 91 as a whole.

Although the printed wiring board 51 of the fifth embodiment is similarto that of the second embodiment, this aspect of the invention is notlimited to such a case. That is, a printed wiring board similar to theprinted wiring board of the first, third, or fourth embodiment may beused.

The electronic apparatus according to the invention is not limited toportable computers and hard disk drives, and the invention can also beapplied to other kinds of electronic apparatus such as a cell phone.Other various modifications can be made of the above-describedelectronic apparatus without departing from the spirit and scope of theinvention.

What is claimed is:
 1. An electronic device comprising: a casecomprising a ground portion; a printed wiring board comprising an edgeportion and a fixing hole located adjacent to the edge portion, theprinted wiring board being housed in the case; a land provided at aposition outside an area extending along the edge portion, the areaincluding a portion between the edge portion and the fixing hole, theland comprising a part extending from a vicinity of the edge portionalong the edge portion; a conductive plating portion covering an innersurface of the fixing hole, the conductive plating portion beingprovided to be continuous with the land; and a screw being screwed inthe fixing hole and electrically connecting the ground portion and theland.
 2. The device of claim 1, wherein the part of the land extendingfrom the vicinity of the edge portion along the edge portion isconfigured to be located more toward the edge portion with respect to acenter of the fixing hole.
 3. The device of claim 2, wherein the printedwiring board comprises a first face that is provided with the land and asecond face that is opposite the first face, and wherein the conductiveplating portion is configured to extend across the first face and thesecond face.
 4. The device of claim 3, wherein the printed wiring boardcomprises a second land that is provided on the second face to becontinuous with the conductive plating portion.
 5. An electronic devicecomprising: a case comprising a ground portion; a printed wiring boardcomprising an edge portion and a fixing hole located adjacent to theedge portion, the printed wiring board being housed in the case; a landprovided at a position outside an area extending along the edge portion,the area including a portion between the edge portion and the fixinghole, the land comprising a part extending from a vicinity of the edgeportion toward a center portion of the printed wiring board; aconductive plating portion covering an inner surface of the fixing hole,the conductive plating portion being provided to be continuous with theland; and a screw being screwed in the fixing hole and electricallyconnecting the ground portion and the land.
 6. The device of claim 5,wherein the printed wiring board comprises a first face that is providedwith the land and a second face that is opposite the first face, andwherein the conductive plating portion is configured to extend acrossthe first face and the second face.
 7. The device of claim 6, whereinthe printed wiring board comprises a second land that is provided on thesecond face to be continuous with the conductive plating portion.
 8. Anelectronic device comprising: a case comprising a ground portion; aprinted wiring board comprising an edge portion and a fixing holelocated adjacent to the edge portion, the printed wiring board beinghoused in the case; a first land provided at a position outside an areaextending along the edge portion, the area including a portion betweenthe edge portion and the fixing hole, the first land comprising a partextending from a vicinity of the edge portion along the edge portion; aconductive plating portion covering an inner surface of the fixing hole,the conductive plating portion being provided to be continuous with thefirst land; an end face of the conductive plating portion having asmaller width than the first land, the end face extending at a portionbetween the fixing hole and the edge portion along the fixing hole; anda screw being screwed in the fixing hole and electrically connecting theground portion, the first land, and the end face of the conductiveportion.